Aluminum base for current collector, current collector, positive electrode, negative electrode, and secondary battery

Abstract

The purpose of this invention is to provide an aluminum base for a current collector, which enables the production of a secondary battery having excellent cycle properties; and a current collector, a positive electrode, a negative electrode and a secondary battery, each of which is produced using the aluminum base. The aluminum base for a current collector has a surface in which at least two structures selected from the group consisting of a large-wave structure having an average opening size of more than 5 μm but up to 100 μm, a medium-wave structure having an average opening size of more than 0.5 μm but up to 5 μm, and a small-wave structure having an average opening size of more than 0.01 μm but up to 0.5 μm are superimposed on one another, wherein a maximum peak-to-valley height Pt of a profile curve of the surface is up to 10 μm.

What is claimed is: 
     
       1. An aluminum base for a current collector, comprising:
 a surface in which at least two structures selected from the group consisting of a large-wave structure having an average opening size of more than 5 μm but up to 100 μm, a medium-wave structure having an average opening size of more than 0.5 μm but up to 5 μm, and a small-wave structure having an average opening size of more than 0.01 μm but up to 0.5 μm are superimposed on one another, 
 wherein each of the large-wave structure, the medium-wave structure, and the small-wave structure has alternating peaks and valleys of a continuously sinuous curve form and an overall profile of the at least two superimposed wave structures also has a continuously sinuous curve form; and, 
 a maximum peak-to-valley height Pt of a profile curve of the surface is up to 10 μm, wherein a peak-to-valley height is measured as the height from a top of a peak of the continuously sinuous curve form to a bottom of an adjacent valley of the continuously sinuous curve form. 
 
     
     
       2. An aluminum base for a current collector, comprising:
 a surface in which at least two structures selected from the group consisting of a large-wave structure having an average opening size of more than 5 μm but up to 100 μm, a medium-wave structure having an average opening size of more than 0.5 μm but up to 5 μm, and a small-wave structure having an average opening size of more than 0.01 μm but up to 0.5 μm are superimposed on one another, wherein each of the large-wave structure, the medium-wave structure, and the small-wave structure has alternating peaks and valleys of a continuously sinuous curve form, and 
 wherein the surface has a maximum peak-to-valley height Pt of a profile curve of up to 10 μm, wherein peak-to-valley height is measured as the height from a top of a peak of the continuously sinuous curve form to a bottom of an adjacent valley of the continuously sinuous curve form, and wherein a surface area ratio ΔS of 20% or more, and a steep area ratio a45 of 5 to 60%, 
 given the surface area ratio ΔS being a value obtained by formula (i):
   Δ S =( S   x   −S   0 )/ S   0 ×100 (%)  (i)
 
 
 
       where S x  is an actual area of 50 μm square surface regions as determined by three-point approximation from three-dimensional data on the surface regions measured with an atomic force microscope at 512×512 points and S 0  is a geometrically measured area, and the steep area ratio a45 being an area ratio of portions inclined at an angle of 45° or more (having an inclination of 45° or more) to the actual area S x . 
     
     
       3. The aluminum base for the current collector according to  claim 1 , having the surface in which at least the large-wave structure is formed. 
     
     
       4. The aluminum base for the current collector according to  claim 2 , having the surface in which at least the large-wave structure is formed. 
     
     
       5. The aluminum base for the current collector according to  claim 1 , having the surface in which the large-wave structure, and the medium-wave structure are superimposed on one another. 
     
     
       6. The aluminum base for the current collector according to  claim 2 , having the surface in which the large-wave structure, and the medium-wave structure are superimposed on one another. 
     
     
       7. The aluminum base for the current collector according to  claim 1 , having the surface in which the medium-wave structure and the small-wave structure are superimposed on one another. 
     
     
       8. The aluminum base for the current collector according to  claim 2 , having the surface in which the medium-wave structure and the small-wave structure are superimposed on one another. 
     
     
       9. The aluminum base for the current collector according to  claim 1 , having the surface in which all of the large-wave structure, the medium-wave structure and the small-wave structure are superimposed on one another. 
     
     
       10. The aluminum base for the current collector according to  claim 2 , having the surface in which all of the large-wave structure, the medium-wave structure and the small-wave structure are superimposed on one another. 
     
     
       11. The aluminum base for the current collector according to  claim 1 , having a thickness of less than 100 μm. 
     
     
       12. A current collector comprising: the aluminum base for the current collector according to  claim 1 , said current collector having an upper surface of continuously sinuous curve form. 
     
     
       13. A positive electrode comprising: a positive electrode current collector using the current collector according to  claim 12  for the positive electrode and a layer containing a positive electrode active material, the positive electrode active material being formed on the continuously sinuous curve form of the upper surface of the positive electrode current collector. 
     
     
       14. The positive electrode according to  claim 13 , wherein the positive electrode active material is a material capable of storing and releasing lithium. 
     
     
       15. The positive electrode according to  claim 13 , wherein the positive electrode active material is a composite oxide containing lithium and a transition metal. 
     
     
       16. The positive electrode according to  claim 15 , wherein the positive electrode active material is lithium cobaltate (LiCoO 2 ). 
     
     
       17. A negative electrode comprising: a negative electrode current collector using the current collector according to  claim 12  for the negative electrode and a layer containing a negative electrode active material, the negative electrode active material being formed on the continuously sinuous curve form of the upper surface of the negative electrode current collector. 
     
     
       18. The negative electrode according to  claim 17 , wherein the negative electrode active material is a material capable of storing and releasing lithium and having a lithium ion-storing and releasing potential of 0.4 V or more with respect to a lithium metal potential. 
     
     
       19. The negative electrode according to  claim 18 , wherein the negative electrode active material is lithium titanate. 
     
     
       20. A secondary battery comprising: a positive electrode, a negative electrode and an electrolyte,
 wherein the positive electrode is the positive electrode according to  claim 13 .